Solar cells are semiconductor devices that convert sunlight into electricity. The principle barrier to wider use of solar cells as a source of electrical power is their cost. To lower the cost of manufacturing solar cells, it is important to develop manufacturing methods which involve very few steps and very little handling and which are capable of very high throughput rates.
One method for lowering the manufacturing cost of solar cells is to reduce the number of overall processing steps. Each step requires a considerable amount of handling, resulting in higher labor cost and adding to the risk of reducing yield. Another method for lowering the manufacturing cost is to simplify each processing step.
By way of background, a crystalline silicon solar cell is made by forming a p-n junction on a silicon substrate, applying front and rear electrical contacts to the solar cell, and covering the front surface of the solar cell with an antireflective coating. The metallization step for the front contact, the metallization step for the rear contact, and the antireflective coating step are performed as separate processes, thereby adding complexity and cost. Also, the antireflective coating step is sometimes performed after the metallization step for the front contact, resulting in the antireflective coating covering the front contact. In such a case, another step, to remove portions of the antireflective coating, is required to access the front contact.
In order to increase light trapping and conversion efficiency, a single crystalline silicon solar cell can be textured using a chemical etching process. When etched, such a solar cell substrate reveals pyramid structures which reflect the incident light back into the solar cell. A polycrystalline silicon solar cell, however, cannot be textured by the chemical etching process due to its various crystallographic orientations. One solution to this problem is texturing an antireflective coating placed on a surface of the polycrystalline silicon solar cell. A known method of texturing an antireflective coating is through a two layer chemical vapor deposition process, which is expensive and slow.
Therefore, a need exists for a method for forming electrical contacts and antireflective coatings on solar cells that is simple and inexpensive.